In a fuel cell, electrical energy and heat am generated by bringing together hydrogen (H2) and oxygen (O2) in an electrochemical reaction. For this purpose, hydrogen and oxygen are fed to the fuel cell, either in their pure form or as fuel gas containing hydrogen and as air. The type of operating gases which are fed to the fuel cell is substantially dependent on the operating environment in which the fuel cell is operated. A fuel cell of a fuel cell system which is operated, for example, in a hermetically sealed space is usually operated with pure oxygen and pure hydrogen. While the fuel cell is operating, these operating gases react to form water (H2O) substantially without any residue, with the result that the fuel cell system generates virtually no exhaust gases.
Depending on their operating temperature, fuel cells are classified as low-temperature, medium-temperature and high-temperature fuel cells, and these categories can in turn be distinguished from one another by virtue of various technical embodiments. A low-temperature fuel cell is understood as meaning a fuel cell which is operated in a temperature range of up to 200° C.
In the case of a fuel cell stack which is assembled from a large number of planar fuel cells, at least one electrolyte electrode assembly, a further interconnector plate, a further electrolyte electrode assembly, a further interconnector plate, etc. are located beneath an upper interconnector plate which covers the fuel cell stack. The electrolyte electrode assembly in this case includes two electrodes, an anode and a cathode, and an electrolyte which is arranged between anode and cathode and is designed as a membrane. In this case, in each case one electrolyte electrode assembly located between two adjacent interconnector plates, together with the interconnector plates which bear against it directly or indirectly on both sides, forms a fuel cell. An interconnector plate is used, inter alia, to electrically connect an electrode of a fuel cell to the electrode of the adjacent fuel cell which bears against the interconnector plate; the electrodes do not have to bear directly against the interconnector plate, but rather may be electrically connected to it, for example by means of contact or protective layers.
The anode gas space of the fuel cell is formed between the anode of a fuel cell and the interconnector plate which adjoins the anode. While the fuel cell is operating, hydrogen (H2) or hydrogen-containing operating gas flows through the anode gas space. On the other side of the interconnector plate is the cathode gas space of the adjacent fuel cell, which is formed between the interconnector plate and the cathode of the adjacent fuel cell. While this fuel cell is operating, oxygen or oxygen-containing operating gas flows through the cathode gas space.
In particular in the case of operation with pure oxygen and pure hydrogen, the interconnector plate is exposed to extremely corrosive operating gases. In addition, in some low-temperature fuel cells, in particular in polymer electrolyte membrane fuel cells (PEM fuel cells), the operating gases are humidified. Therefore, the interconnector plate is exposed not only to the operating gases but also to water. Water and, for example, pure oxygen form an extremely aggressive medium at the operating temperature of low-temperature fuel cells.
WO 00/59056 has disclosed a fuel cell having an interconnector plate made from a chromium-based alloy. However, an interconnector plate of this type has the drawback of being relatively brittle. It is therefore difficult to deform and has very poor welding properties, and moreover must be made relatively thick if the required stability is to be achieved.